Composite piston



Junezo, 1939. SUMMERS 2,162,830

COMPOSITE PISTON Filed Dec. 3, 1934 2 Sheets-Sheet l 7 I ll June 20, 1939. Ci SUMMERS COMPOSITE PISTON Filed Dec. 3, 1934 2 Sheets-Sheet 2 This invention ha Patented June 20, 1939 PATENT OFFICE COIVIPOSITE PISTON Caleb E; Summers, Pontiac, Mich, assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application-December 3, 1934, Serial No. 755,651

internal combustion engines, and

with improvements on the claimed in my prior Patent July 15, 1930.

4 Claims.

s to do with pistons used in particularly piston disclosed and No. 1,770,818, granted The piston herein disclosed is of the composit consists of a cast head, of

ite type, that is,

aluminum or other lig pressed metal such as enough to be readily ht metal, and a skirt of steel; Sheet metal soft formable is known to be very poor as a bearing metal against the cast iron of the cylinders s vide the skirt with a coating ofmetal as disclosed in my pr No. 18,814, granted May Since the metal of the piston head coeflicient of expansion than that the design of the piston shoul permit the necessary exp out distortion of the skirt. This is accomplished according to the present invention by providing longitudinal slots head over which of course, not feasible portions of the head bearing bosses so ing, to permit the Another improvemen of attachment of accomplished by grooves in the skirt, pr

tudinally and ansion of the o it is preferable to prosoft bearing ior patent, Reissue has a higher of the skirt d be such as to head within the lower portion of the the skirt is telescoped. It is,

to provide slots in the adjacent the piston pin is necessary to relieve the corresponding portions of the skirt, as by grindrequired expansion.

the

t has to do with the means head and skirt. This is providing inwardly pressed By locating eferably running longilocatedv outside of the effective rt. Plates secured to the against pord are secured thereto by the connecd skirt outside of the pise latter is free from dish would ordinarily result ion and at the same time that the parts may be readily secured together in production.

In the drawings:

Figure 1 is a parts in section.

Figure 4 is a side el a section on line 6-6 Figure 'I is a section on line longitudinal vertical sectionthrough the piston.

Figure 2 is a section on line 2--2 of Figure 1.

Figure 3 is a side elevation of the piston with evation of the piston head bottom plan view of the head oi! Figure 5. of Figure 4.

Figure 8 is a perspective view of the piston head attaching plate.

10 indicates the cast vided with grooves I2 head of the piston proto receive the usual pis-' ton rings and having a cylindrical surface it 5 apertures in the bosses are preferably provided with inturned tongues 24 as shown in Figures 2, 3 and 8, alternate tongues being bent in OPPO, site directions. Plates 22 are likewise provided with pierced openings openings forming integral flanges 25 about them.

It will be noted that the upper portion of the skirt I6 is in telescopic engagement with the cylindrical surface M of the piston head. To permit the greater expansion of quired by the characteristics of the material of which it is made, without distortion of the skirt, there are provided in the cylindrical portion ll of the head on both sides of the axis of the wrist pin bosses of slots on each side of the axis of the wrist pin bosses is preferably arranged within an arc of approximately 108 whose ends are-equidistant from the axis of the wrist pin bosses so as not to the head. The slots 26 permit expansion of the head of the piston without distortion of the skirt since the metal can expand into the slots.

Referring to Figure 2 it will be noted that the 23, the metal from the 20 the head re- 25 a number of slots 26. The set 30 to reduce the strength of connection or the bosses 35 skirt I6 is provided with inwardly pressed V- 40 shaped ribs 28 adjacent the piston pin bosses. These ribs extend longitudinally of the piston, but, as best shown of the upper and lower edges of the skirt to provide in the first instance the surrounding the lower part ll of the head of the piston and to provide the bearing portion 30 at the bottom of the skirt. The edges of the plates 22 overlap the sides of the ribs 28 and are prefin Figures 1 and 3, stop short telescopic portion 45 erably secured thereto by welding as best shown 5 in Figures 1 and 2. This method of attachment is well adapted for production and has the additional advantage that the welds are not formed on a part of the bearing surface of the piston. Plates 22 also serve as reinforcements to hold 55 the bearing portions of the piston wall against distortion.

The skirt may be formed to provide circumferential oil grooves as shown at 32.

It will be noted by reference to Figure 3 that the skirt is spaced from the ends of the piston pin bosses l8, although it is snugly fitted about the portion of the head directly above the bosses. Since this portion of the head is not provided with slots, it is necessary to relieve the skirt by grinding off a few thousandths to permit the necessary expansion of the metal.

The parts of the piston may, of course, be made of a variety of materials. However, it is preferable to employ for the heads some light material such as aluminum or magnesium alloys and to employ for the skirt sheet metal of suflicient softness to be easy to shape. Inasmuch as such sheet metal does not have proper qualities to make a good bearing surface with cast iron it is desirable to coat it with soft metal as shown at 34 to provide a bearing surface. This metal may be applied by electroplating or other methods as described in my prior Reissue Patent No. 18,814. Any of the kinds of soft bearing metal referred to in that patent may be used.

The improved piston will be found to be light in weight, and will at the same time maintain a good fit in the cylinder. The bearing qualities of the soft metal coating on the skirt will insure long service and prevent seizing and scoring particularly when used in combination with the slotted portion M of the head which prevents distortion of the skirt. The means of attachment of the head to the skirt is simple and readily accessible for the welding operation.

I claim: I

1. A piston comprising a cast head having integral piston pin bosses, plates inseparably interlocked with the metal of the bosses and extending at right angles to the axis of the piston pin bosses, a sheet metal skirt having its upper portion in telescoping engagement with the lower portion of the head, the portion of the head overlapped by the skirt between the bosses being slotted throughout its length to permit expansion of the head without distortion of the corresponding portions of the skirt, the skirt being provided with inwardly pressed trough-shaped longitudinal ribs whose longitudinal edges are joined to the skirt engaging the plates and welded thereto, said ribs and plates constituting a reenforced connection between the head and skirt, and a coating of soft bearing metal on the outer bearing surface of the skirt.

2. In a piston, a cup-shaped head which is made of a metal which has a relatively high temperature coeflicient of expansion, ears which are integral with and project from the open end of the head in the direction of the longitudinal axis of the piston, a skirt which is made of a metal which has a relatively low temperature coefficient of expansion and surrounds the projecting ends of the ears and an approximately cylindrical portion of the outer side wall of the open end of the head and always fits snugly around the latter, means which interconnects the skirt and the head through the ears, and slots which extend lengthwise of the piston in the portion of the side wall of the head which is located between the ears and surrounded by the skirt.

3. In a piston, a generally cup-shaped head in which there are provided packing ring grooves, wrist pin bosses carried by the head, a skirt which is telescoped and fits snugly around a portion of the head which is of substantially uniform circumference throughout its length, and slots which extend lengthwise of the piston through the side wall of the head from its lower end to apoint above the upper end of the skirt but below a packing ring groove to prevent expansion of the head between the wrist pin bosses distorting the skirt.

4. In apiston, a generally cup-shaped head in which there are provided packing ring grooves, wrist pin bosses carried by the head, a skirt of which a portion is telescoped and fits snugly around a portion of the head which is of substantially uniform circumference throughout its length, and slots which extend lengthwise of the piston through the side wall of the head from its lower end to a point above the upper end of the skirt but below a packing ring groove to pre-. vent expansion of the head between the wrist pin bosses distorting the skirt, the portion of the skirt which is telescoped around the mentioned portion of the head being of smaller external diameter in the line of the wrist pin bosses than at a right angle thereto.

C SUMMERS. 

